That's really weird. I agree the tank probably isn't fully cycled but it shouldn't have had that immediate affect on your oscar. Did you use water conditioner? There must be something either chloramines or some toxin that would cause him to react badly so fast. At least it sounds from your post like the reaction was fast. How long was he in there hiding before looking bad and going belly up?

I used 5tsp of conditioner per instructions on the bottle.

he hid behind the airline for like 20 mins....long enough for me to smoke two cigarettes and get really anxious. Then he moved out of there and started swimming sideways for a few mins then started going belly up. Thats when i yanked him back into the old tank. He acted funny for about 5 mins after that then was right back to his normal behavior. I did notice something floating in the net that looked like some of his food after I put him in the new tank like he had thrown it up. However, I didn't think this to be noteworthy before because if somebody stuck a net in my living room and scopped me up and tossed me somewhere new, I'd probably puke too.

the tank had been previously used as a reptile tank by my friend so I cleaned it the same way I clean any new tank: bleach, rinsed it out, cleaned it out again with water then flushed it with warm water before putting in the new rocks and such. the pH is a little high (around 8 ) but he should be used to that because the tank he's in now sits at about the same pH because of his waste.

Sure you rinsed the bleach real well? It's really strange and unless the temp of the water or the pH were wildly different from what he was use to I can't see them causing the reaction you witnessed. Nor would the fact that the tank isn't cycled cause such a quick reaction.....he would have to live in the tank for awhile and build up ammonia before the uncycled tank would be a problem. Maybe he got shaken up or hurt/disoriented during the transfer? Very weird. I'd watch him real closely when you try to transfer him again 'cause something about that wasn't right.

I guess its possible I didnt get all the bleach out, but wouldn't the presence of chlorine of that type put the pH thru the roof? Even still, If the bleach is the culprit is there any other remedy besides draining the tank, recleaning and setting it up again? I'd hate to make him wait another week to get into his new home, but it's better that then lose my favorite pet.

Is there any way I can tell for sure thats the issue? (say sacrificing some bait store minnows to the death tank)

*EDIT*

He was def. mad when i started chasing him around the old tank with the net. I'd imagine he was very disoriented and a whole lot angry to be taken from the home he's lived in since he was the size of my thumb. However, there's no way I'm going to be able to move him without getting him irritated. He doesn't seem to be injured and his appetite came back within an hour, so I'm going to say he's physically fit.

I'm not sure but I think the water conditioner would have neutralized the bleach even if it wasn't fully rinsed and it's very unlikely that would be the cause since rinsing off bleach is fairly easy and not a huge deal. Any weird decorations? Maybe he just had a neurotic fit! It just sounds like a toxic reaction but maybe he was shook up from the transfer. You said he was pretty "violent" when you tried to catch him so I guess that could be it. I certainly wouldn't tear down the entire tank at this point but I might wait a few days before trying again. Are you aerating the new tank?

Also how big is your oscar? Make sure you take everything out of the old tank before you try and net him so there is nothing for him to scratch or hurt himself on. Also make sure your net is much bigger than the fish. If there are any decorations he is used to from the old tank put them in the new one before you put him in so he has something he is used to right away. I'd also keep the lights off for the first couple hours after moving him so he has a chance to get use to the much larger space without the stress of lights.

i decided to dump a few $1.34/dozen "test pilots" into the tank to see if they acted the same. To my surpise, they all aive and well going on 7 hours now. This leads me to the conclusion that the symptoms i saw in my oscar were nothing more than shock and mental trauma. I plan to let those guys live a few days in there and move my oscar, frog and pleco in sunday with the use of pet store fish bags to minimize shock.

and as a reward for not dying in the tank transfer, they'll have all the crappies they can eat